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Unformatted text preview: 994 AH84001 joined the Mars club!
History: formed from magma ~ 4.5 × 109 yr ago !
Fractured by meteorite impact!
Carbonate globules, … !in cracks ~ 3.6 × 109 yr ago !
Blasted off Mars by impact
! 17 × 106 yr ago !
Fell to Earth
! 13 × 103 yr ago!
! So, known to be from Mars before issue of life arose! Signs of Life?!
McKay et al., Science, 273, 924 !(Aug. 16, 1996)!
Found in fractures - ~ 3.6 × 109 yrs old!
When water existed!
1. PAHs - can be produced by breakdown of !
!Contamination from Antarctic Ice?!
!Different mixture of PAHs!
!Not necessarily biological - also found in space,!
!interplanetary dust, other meteorites, …!
!Associated with carbonate globules! Carbonate globules! Evidence of liquid water
is disputed! 2. Carbonate Globules (50 µm across)
! cores of !
manganese! & rings of iron carbonate!
! and iron sulﬁde!
! similar to globules associated with bacterial!
! action in liquid on Earth!
!Can form without bacteria on Earth!
!Dispute about temperature at which globules
formed ! ! 3. Magnetite Grains!100 nanometers (nm)
!(100 × 10-9 m = 0.1 µm)
Shapes similar to !crystals produced by bacteria on Earth!
Other shapes seen by other workers!
Whisker shapes suggest formation in hot fumaroles!
4. ! Fossilized Bacteria?! !!With scanning electron microscope, see !
!!bacteria-like shapes (20 - 100 nm long) similar to those
seen in Earth rocks near hot springs !! (R. Folk - UT Austin) described as nanobacteria !
~ 10 - 100 × smaller than normal bacteria!
Are these artifacts of process used by microscope (gold coating)?!
Need to section and look for membrane - very difﬁcult! Martians??! Later Developments!
1. Several studies support lower temperature!
!for carbonate globule formation - consistent with!
2. Folk ﬁnds similar shapes in Allende meteroite !
!(not from Mars)!
2011: Claim of cyanobacteria-like fossil organisms
in several carbon-rich meteorites.! 4. Bada et al., 1998, Science 279, 362 Found amino
acids, suggestive of terrestrial contamination!
5. Many more meteorites from Mars being found.!
!! Venus Express Orbiter!
• Venus Express Orbiter, an ESA mission!
– Launched Nov. 2005, arrived Apr. 2006!
– Studying atmosphere, surface with radar!
– Learning about methods of water loss!
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This note was uploaded on 04/05/2013 for the course UGS 302 taught by Professor Staff during the Spring '08 term at University of Texas.
- Spring '08